Section A was taken during late December along a north-south line 

 which closely followed the 100° W. meridian. The sharp break in slope 

 •of the surface-temperature plot is apparent at about 61° 47' S., with a 

 mean temperature of 3-2° c. on the steepest part of the slope (see Table 1). 

 This is a higher temperature than was observed at the convergence on 

 any of the other sections. The surface temperature decreases about 

 2-2° c. in a" distance of 20 miles. 



In section B, which lies 40° to the west of section A, the large tempera- 

 ture gradient indicative of the ' convergence was found much farther 

 north, at 60° 24' S. The obser^^ations are more closely spaced in this 

 section and consequently give a more complex temperature structure. 

 The temperature gradient at the convergence on this section is about 

 2-0° c. in 15 miles. 



Sections C-1, C-2, and C-3, which are all in one locality, give indica- 

 tions of seasonal changes in the surface temperatures at the convergence. 

 In section C-1 the convergence was found early in the season at 62° 46' S., 

 with a mean temperature of about T8° c. This is the most striking break 

 in temperature found. The decrease is 2-5° c. in a distance of 10 

 miles. Section C-2, taken fifty-four days later, shows the convergence 

 at 63° 50' S., with a mean temperature of 2-7° c. This indicates that the 

 convergence had moved south about 64 miles and the temperature at 

 the convergence increased by 0-9° c. The temperature gradient decreased 

 to T8° c. in 30 miles. The third section in the same longitude shows 

 that the convergence moved back to the north to about 63° 20' S., with 

 a mean temperature of 2-8° c. This northerly displacement amounts 

 to 30 miles in a period of fourteen days. The surface temperature 

 gradient here is 2-8° c. in approximately 80 miles. A summary of the 

 surface temperature characteristics at the convergence is contained in 

 Table 1. 



Table 1- 



-LocATioN OF Surface Temperature Sections Across the Antarctic 

 Convergence 



Vertical Temperature Section 



The convergence should be marked at subsurface depths by a con- 

 tinuation of the sharp gradients found at the surface. Another im- 

 portant indication of the northern limit of the antarctic region, and 

 hence of the location of the Antarctic Convergence, is the position of the 

 northern boundar\' of the subsurface temperature minimum which 

 develops in summer. This temperature minimum marks the remainder 

 of the winter-cooled layer. During the period of active cooling a surface 

 layer of nearly homogeneous water develops throughout the Antarctic 



293 



